Let's suppose we are using the exponential ElGamal as a public-key encryption scheme, so that we encrypt $g^m$ instead of $m$, for some generator $g$. Let $x$ be the private key, and $h=g^x$ be the ...

Could a variable participant lottery system cryptographically prove that they have zero knowledge of the outcome of a draw?
Participants do not choose numbers in this lottery and winning numbers are ...

If Alice encrypts two messages $a$ and $b$, such that $x=E(a)$, $y=E(b)$. Can Alice prove (without revealing $a$, $b$ or the private key) that $a = b$?
Obviously the proof must not be too long and it ...

In the classic description of Zero Knowledge Proof of Knowledge, Victor must wait outside the entrance to the cave while Peggy goes to the fork and choose a side. It's only once Peggy has entered a ...

Alice has a bank account number, but has forgotten which bank it is for. There are 4 banks, run by Bob, Carlos, David, and Eve.
She could find out by going to all of the banks and asking if they have ...